The use of phenolics as disinfectants is well established in the art, such as is represented by U.S. Pats. 1,980,966 to Blocke; 2,572,855 to Guy; 2,802,881 to Rickert; 3,002,883 to Butt et al.; 3,215,596 to Moyle et al.; and 3,257,273 to Shambough et al., as well as by British Pats. 789,713 to Schuelke and Mayr; 872,900 to pearson et al.; 927,255 to Wright; and 1,150,966 to Bondy et al. As can be seen from this representative sampling of the prior art, phenolic disinfectants are generally comprised of mixtures of substituted phenols solubilized with alkali, anionic detergents, soaps and the like and, in addition, frequently contain alkaline phosphates, small amounts of a chelating agent, solvents, perfumes and the like. For example, the British Patent to Wright (927,255) discloses utilizing ortho phenylphenol with other phenols in compositions which contain soap as the detergent, the detergent being derived from the saponification of castor oil with potassium hydroxide to obtain potassium ricinoleate. This patent also discloses the use of oleic acid to react with excess alkali.
British Pat. 1,150,966 to Bondy et al. also reveals the use of ortho phenylphenol in admixture with other phenolics to provide a solid composition in tablet form which is intended for use, after being dissolved in water, as a household detergent, such as for dishes.
The above two British prior art references have been singled out as they ostensibly appear to reflect the concepts of this invention. It is important to bear these references in mind for it will be seen, as revealed in more detail hereinafter, that the presence of soap is detrimental to the function of the disinfectant of the invention and that unless one employs only particular types of phenols with ortho phenylphenol and these types only at the proper levels, the effectiveness of the phenolic disinfectant of the invention against Staphylococcus, Salmonella and particularly the troublesome Pseudomonas species in hard waters will not be achieved.
It is also well known to those skilled in the art that the inclusion of small amounts of an anionic detergent will aid in the performance of these phenolic disinfectants but that higher ratios of the detergent to the phenolics interferes with their effectiveness. It is further known that the alkali content of these phenolic disinfectant compositions has to be controlled so that the pH of the use dilutions prepared therefrom is not significantly higher than the pK of the phenolics employed in the disinfectant composition.
More recently, phenolic disinfectant compositions have been comprised of high activity phenolics alone or of mixtures of high activity phenolics with intermediate or low activity phenolics.
A good general survey of phenolic compounds has been presented by R. F. Prindle and E. S. Wright in Disinfection, Sterilization and Preservation by Lawrence and Block, Lee and Febiger, Philadelphia, 1968.
For purposes of this invention, the term "phenol coefficient," as employed throughout the application and in the appended claims, should be understood as being based upon the following definitions: a high activity phenolic is one having a phenol coefficient of about 150 or higher at temperatures of from about 20.degree. C. to 37.degree. C. against S. aureus. Similarly, an intermediate activity phenolic is one having a phenol coefficient of from about 25 to 150, and a low activity phenolic is one having a phenol coefficient of less than 25; the phenol coefficient being obtainable by the methods set forth in the Methods of Analysis of the Association of Official Agricultural Chemists (AOAC), 10th Edition.
The disinfectant activity of disinfectants is determined and measured by the official USDA test as described on pages 82-84 of the AOAC, 10th edition, hereinafter referred to and identified as the Use Dilution Confirmation (UDC) test, and is employed to test disinfectants which are miscible with water to confirm phenol coefficent results, and to determine maximum dilutions that are effective for practical disinfection. In general, the test involves providing an organism to be tested, such as S. aureus, S. choleraesuis, Pseudomonas aeruginosa and the like, and preparing sterilized ring carriers. The ring carriers are placed into contact with the organism to be tested and are then placed on a petri dish to allow the organism to dry as a film on the ring. The contaminated carriers are then placed in a solution of the germicide to be tested for a 10 minute exposure interval and the results are reported in groups of 10 rings.
The disinfectant activities are reported at the recommended dilution of the germicides being tested against S. aureus, S. choleraesuis, and Pseudomonas aeruginosa; distilled water is specified to dilute the germicidal products. However, hard water can be used as the diluting medium in addition to distilled water, and if pass results are obtained, additional efficacy claims can be made for the product.
Generally, commercially available phenolic disinfectant compositions fail against Pseudomonas organisms in waters containing as little as 100 p.p.m. AOAC hardness and even fail in city water that is ordinarily considered to be "soft"; that is, having an AOAC hardness of as little as about 50 p.p.m. Consequently, the claimed activity of these phenolic disinfectant products against Pseudomonas organisms cannot be completely relied upon to actually disinfect against Pseudomonas organisms under actual use conditions unless they are specifically guaranteed for use in water other than distilled water.
It is known that ortho phenylphenol has a relatively low phenol coefficient and is, therefore, relatively ineffective against S. aureus and S. choleraesuis. However, ortho phenylphenol is about as effective, on a weight basis, against Pseudomonas organisms as are the high activity phenolics. Since the solubility characteristic of a phenolic in a use dilution limits the amount of any one phenolic that can be incorporated in a product, it has been the practice to include some ortho phenylphenol in product formulations in order to enhance the performance of these products against Pseudomonas. However, the ortho phenylphenol content is usually kept below the total amount of other phenolics present in the product and, rarely has it been increased to a level approximately equal to that of the other phenolics present. It has been possible, therefore, to provide compositions containing, in use dilution, about 500 p.p.m. or more of combined high activity phenolics and ortho phenylphenol, plus a small amount of a chelating agent, which are effective against Pseudomonas in distilled water.
In attempting to formulate products that would pass against Pseudomonas in hard water, however, a different problem has been encountered. Attempts to increase the amount of high activity phenolic or decrease the recommended dilution were not effective since the solubility limit of the phenolic was reached before enough high activity or intermediate activity phenolics could be added to accomplish the desired result. Increasing the amount of ortho phenylphenol at the expense of the other phenolics was also found to be ineffective since the amount needed to disinfect against Pseudomonas would still be inadequate against other test organisms such as Staphylococcus and Salmonella.